Working & Display of Fishfinder
There is a transmitter located on the ship, which sends signals in the waves. The SONAR system uses the aspect of echoes to reflect back the waves to the transmitter. The reflected waves are recorded and a signal is sent to the screen.
In order to make sure the signals received are not false signals, the waves coming after getting reflected from fishes are displayed differently as compared to those coming from stones, corals or other obstructions. Thus, echoes differ in size and form when there are fishes in the water unlike when the water is clear of fishes. Things other than fishes are displayed with different symbols.
The display screen shows the presence of a fish in the water with the help of a symbol in the form of a fish. This display sometimes changes to become arches on the screen when the boat is cruising over that part of the water where the fishes are located. However, the display of the fish is unique so that the person monitoring the digital screen will not have any confusion regarding the presence of fishes and other underwater plants and stray weed.